Hiding in Plain Sight

January 1, 2011
By Mandy Calkins
Comb through a heap of sargassum − that familiar brown seaweed that piles up on Atlantic and Gulf Coast beaches − and you may find a fish that is a true master of disguise.
Sargassum fish can almost disappear into their habitat. Credit: Don DeMaria

The little sargassum fish is named for its habitat: the floating masses of sargassum algae that drift on the ocean’s surface. This fish mimics its surroundings in both color and form. Measuring up to seven inches in length, the sargassum fish is creamy brown with irregular dark bars, and its appendages have a fringed, weedy appearance, allowing it to all but disappear into the tangles of sargassum it inhabits. The creature has even adapted its movement to its environment: though it can swim if needed, the sargassum fish uses its pectoral fins like a pair of arms to maneuver through the seaweed jungle.

Sargassum fish spend their entire lives among drifting mats of seaweed − and why not? The mats are shelter
for many species that make tasty prey for this ambush hunter. Its camouflage allows it to sneak up on shrimp and smaller fish − including its own species! When the sargassum fish is in danger, it can leap on top of the seaweed mat for a quick escape from larger fish below.

This exquisitely adapted fish can spend its entire life among seaweed in the open ocean, but it often gets blown on to shore with storms. That’s where beachcombers can spot it in masses of seaweed − if they look closely enough.